California Laboratory for Atmospheric Remote Sensing
Methane (CH4)
We determined the emissions of CH4 in LA from 2011to 2019, extending from He et al. (2019), using CLARS-FTS observations based on a tracer-tracer ratio method with CO2 emissions. We show that the pattern of CH4 emissions contains both seasonal and non-seasonal contributions. We find that the seasonal component peaks in the winter and is correlated (R2=0.50) with utility natural gas consumption from the residential and commercial sectors and not from the industrial and gas-fired power plant sectors. The non-seasonal component is (14.0 ± 1.3) Gg CH4/month. If the seasonal correlation is causal, about (1.8 ± 0.18) % of the commercial and residential natural gas consumption in LA is released into the atmosphere. This report updates these numbers, which are different from He et al. (2019), with two more years of CLARS observations and updated background calculation. Identification of the sector(s) responsible for the CH4 emissions and their temporal and spatial variability is a key step in achieving the goals of emission reduction.